A population-based study of asthma and wheeze in school-age children

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Occupational exposures to farming activities are known to be associated with respiratory symptoms in adults. It is not known if exposures to similar activities are also risk factors for respiratory symptoms in children. In order to assess the risk of asthma and wheeze in children exposed to farming activities, a cross-sectional survey was conducted with parents of 2374 school children attending Grades 1 to 5 in the west-central farming region of Saskatchewan, Canada. The overall response rate to the survey questionnaire was 80.5%. The prevalence of ever asthma was 10.2% and the prevalence of ever wheeze excluding asthma was 10.5%. In the past year, 1517 children (63.9%) had exposures of more than one hour at a time to farming activities. After adjusting for potential covariates, the risk for asthma and current asthma with exposure to regular farming activities was 0.70 (CI: 0.49-0.99) and 0.58 (CI: 0.38 to 0.90), respectively. The risk of current wheeze for children exposed to regular farming activities was1.92 (95% CI: 1.23-2.98). For children who lived on farms or acreages, the risk of wheeze with regular farming activity was 2.43 (CI: 1.52-3.92) and with any farming activity was 5.11 (CI: 1.58-16.55). Parental report of asthma by questionnaire was validated with a random sample of 30 children (males = 18; females = 12) with questionnaire report of asthma or wheeze who were matched on sex and grade to 30 asymptomatic children. Accompanied by parents, all children underwent a clinical examination by a respiratory physician. Mean peak expiratory flow rates (PEFR) were measured prior to a free-running exercise challenge and again at 5, 10 and 15 minutes post exercise. There was 89% agreement between questionnaire reported asthma and the physician diagnosis of asthma (Kappa = 0.77). Children with questionnaire reported asthma and/or wheeze and children who were classified as having asthma on clinical assessment had greater percent reductions in mean PEFR at 10 minutes following exercise than did their controls (p $